Eleven leading al-Qa'eda suspects were transferred to a new CIA facility in North Africa, current and former officers told ABC television.

Condoleezza Rice and Angela Merkel after a tense meeting at the Chancellery in Berlin

The allegation emerged as Miss Rice, the US secretary of state, had an awkward meeting with Angela Merkel, the new German chancellor.

It had been billed as the start of a new era of relations but instead it was dominated by the transatlantic row over the CIA's activities in Europe, and one case in which the CIA allegedly mistook a German citizen for a terrorist suspect and abducted him.

The Bush administration has refused to confirm or deny that the CIA runs "black sites" in Eastern Europe to hold terrorist suspects outside the reach of US law. The allegations were made in the Washington Post last month.

The controversy intensified with the release of more detailed allegations on ABC News yesterday. It claimed that 11 top terrorist suspects were held on a former Soviet air base in Eastern Europe until some time last month.

Several of them were later held at a second base, CIA officials told the network. They were all moved to North Africa after the Post's report.

Ten of the detainees were subjected to the harshest interrogation techniques allowed, the network alleged.

Miss Rice sought to mollify critics in Germany, the first stop of her four-day tour, yesterday when she admitted America had made "mistakes" in its fight against terrorism. The Bush administration would, she said, do everything it could to rectify them.

A large part of her talks with Mrs Merkel concentrated on the case of the German national, Khaled el Masri. He was allegedly flown by the CIA from the Balkans to Afghanistan, held for five months and released because he was the wrong man.

"I am happy to say that we spoke about the individual case, which the US administration has accepted as a mistake," Mrs Merkel said.

US officials later however bridled at Mrs Merkel's comments. They said Miss Rice had informed Germany about Mr Masri's detention and release. "We are not quite sure what was in her head," one senior US official said, referring to the German chancellor.

The official added that Mrs Merkel might have drawn her conclusion from media reports rather than from communication with the US government.

The row was the worst possible conclusion to a meeting that both countries had hoped would usher in a friendlier period of relations following the appalling relationship between Gerhard Schröder, Mrs Merkel's predecessor, and President George W Bush.

Mrs Merkel stressed that while agreeing on the need to fight terrorism she did not support any illegal methods.